Successful machining trials for full-size radial plates

The side radial plate completed by CNIM in Toulon, France. Photo courtesy of CNIM.

Good news for the toroidal field coil team at the European Domestic Energy Fusion for Energy (F4E): the two companies assigned to the manufacturing of the full-size radial plate prototypes, CNIM and SIMIC, have reported the successful completion of the machining for one side and one regular radial plate.

The radial plates that hold the conductor of the toroidal field coils are very complex 8.5 x 15 metre, D-shaped stainless steel structures with grooves machined on both sides along a spiral trajectory. Each toroidal field coil is composed of seven double pancake modules. Each double pancake is composed by a radial plate within whose grooves the insulated conductor is embedded. Each coil contains five regular radial plates (with 12 grooves per side) and two side radial plates (with respectively 9 and 3 groves on the two sides).

The side radial plate prototype was manufactured by CNIM based in Toulon, France utilizing seven stainless steel forged plates made of 316LN and butt welded with local vacuum electron beam technology. Each section is fully machined to the final tolerances except the welded areas.

The regular radial plate prototype was manufactured by SIMIC in Camerana, Italy utilizing 16 sections of hipped (hot isostatic pressure) 316LN stainless steel butt welded by narrow gap TIG. Each section was pre-machined before welding leaving extra material; the whole radial plate was then machined with a large portal machine, now belonging to F4E.

On both radial plates the required, and very demanding, tolerances were achieved. This success demonstrates the feasibility of the radial plate for the first time, and also qualifies two different technologies for manufacturing.

F4E is now preparing the launch of the tender procedure for the production of 70 radial plates needed to produce the 10 coils that represent the European share to the ITER toroidal field magnet system.

A special thanks goes to Eva Boter and Marc Cornelis for their big contribution to this "success story."